1. Field of the Invention
The present invention relates to a device wafer processing method of processing a device wafer having a plurality of devices formed on the front side.
2. Description of the Related Art
The back side of a device wafer having a plurality of devices formed on the front side is ground to reduce the thickness of the device wafer to a predetermined thickness. Thereafter, a transfer step is performed in such a manner that a dicing tape as an adhesive tape is attached to the back side of the device wafer to thereby mount the device wafer through the dicing tape to a ring frame, and a protective tape attached to the front side of the device wafer prior to grinding the back side of the device wafer is next removed. Thereafter, the device wafer with the dicing tape is divided into individual device chips by using a cutting apparatus or a laser processing apparatus, for example. In mounting the device wafer to the ring frame, it is necessary to establish a predetermined positional relation therebetween. Conventionally, the device wafer is positioned with respect to the ring frame on the basis of a mark indicating the crystal orientation of the device wafer.
However, in the case of forming a cutout such as a notch and an orientation flat on the outer circumference of the device wafer, the number of devices that can be formed on the device wafer is decreased. In particular, the orientation flat is a large cutout. Accordingly, in the case of a wafer having a diameter of eight inches or 12 inches widely used in recent years, the orientation flat is replaced by the notch as a smaller cutout. However, in the case of a wafer having a notch formed on the outer circumference, there is a possibility that the wafer may be cracked from the notch in a heat treatment step or the like to be performed in forming the devices on the wafer. To cope with this problem, there has been examined a method of forming a mark indicating the crystal orientation on the back side of a wafer in place of the notch.